Dispensing pumps are known in the prior art for administering various liquids, including medicants, lotions, oils, perfumes, etc. The majority of dispensing pumps are positive displacement pumps in which the precise size of an administered dose is not considered critical. However, there is a subset of dispensing pumps that satisfy applications where the dose size is considered critical and repeated consistent dosing within narrow tolerances is required. For example, in U.S. Pat. No. 5,881,596 entitled “MICRODISPENSING OPHTHALMIC PUMP” which issued on Mar. 16, 1999 to the inventors herein, discloses a pump capable of repeatedly delivering doses as small as 5 microliters. Wherever repeated consistent dosing is required, especially with microdoses, such as that delivered by the pump of U.S. Pat. No. 5,881,596, the ingress of air into the pump mechanism and/or liquid path through the pump may cause dosing irregularity and/or pump stalling. The harmful effects of the ingress of air stem largely from its compressibility. If excessive air is introduced, the pump may require re-priming, which is not desirable, or may be impossible. Even where pumps are insensitive to this problem because the dose volume is sufficiently large that delivery of a dose will cause the air to be purged, the dose volume is nevertheless affected and this is undesirable in certain instances.
A common cause of the ingress of air into a dispensing pump is the exposure of an inlet end of a dip tube to air entrapped in a liquid reservoir. The inlet end is exposed generally because the dispensing pump is oriented in a gravitationally non-upright position and/or a low level of liquid is present in the reservoir.
Separately, with the majority of dispensing pumps, the alignment of the dispensing pump and a target is not critical. There are, nevertheless, devices that require to be carefully aligned with a target prior to delivery of a dose. For example, the pump of U.S. Pat. No. 5,881,596 is capable of delivering a dose of ophthalmic medication to an eye. The alignment of the eye, in particular a portion to be treated (e.g., iris, pupil, cornea), with the dispensing pump is an important factor in maximizing the effectiveness of the medication.
It is an object of the subject invention to provide accessories for a dispensing pump which will prevent the ingress of air thereinto.
It is also an object of the subject invention to provide accessories for aiding in the alignment of the dispensing pump prior to actuation of the dispensing pump, and delivery of a dose.